Clients use distributed computer environments to perform a variety of tasks across multiple applications. For a typical task, a client sends a request to a distributed computer environment, which returns a response to the client. While this seems simple enough, there are actually several intermediate steps involved in executing such a request. First, a user or an application initiates the client request by sending the request to an application server. The application server is a computer acting as an intermediary between the client and other resources making up the distributed computer environment. The application server may perform such tasks as verifying the client's security credentials and determining which resource on the distributed computer environment is appropriate for executing the client's request. Second, the application server forwards the request to the appropriate resource on the client's behalf. Third, after the request executes on the appropriate resource, the application server sends the response to the client.
Certain fragment markup and assembly technologies, such as EDGE SIDE INCLUDE (ESI), DELTA ENCODING, and other fragment markup and assembly engines allow for the fragmentation of requests under certain circumstances at the application server. Often, requests can be split into multiple smaller tasks, or “fetches” and distributed across multiple resources. After all the fetches are executed, the fragmented responses are reassembled and returned to the client. Fragmentation allows for more efficient use of resources and for lower cycle-times on a distributed computer environment. Once all the fragments are executed, the responses are aggregated and returned to the client.
When fragments execute in sequence, there can be a long delay from the time the request is made until the fragmented responses are aggregated and returned to the client. To shorten the overall time needed to execute a set of fragments, methods have been developed to allow request fragments to execute asynchronously. With asynchronous execution, fragments can be executed simultaneously, or in any order, reducing the overall time needed to execute a fragmented request.
One example of dispatching asynchronous threads is disclosed in U.S. Pat. No. 7,003,570 owned by BEA Systems, Inc. The '570 patent discloses a system that operates on an application server that provides for asynchronous processing of request fragments. After all the request fragments are executed and responses returned to the application server, the responses are aggregated and returned to the client from the application server. But aggregation takes place at the application server, and application server system resources are tied up.
In addition to tying up application server system resources, current asynchronous fragment execution systems require that the client wait until all the fragments are executed and aggregated before receiving a response. Depending on the complexity of the original request, the client may have a long wait before receiving a response. Meanwhile, the application server is tied up with the execution thread until the entire request is executed. The delay is particularly acute when executing multiple fragments and aggregating the fragmented responses before returning a response to the client. Therefore, a need exists for a way to free up the execution thread and shift the burden of retrieving and aggregating the response to the client, freeing up application server resources while preserving in a fragment any context included in the original request.